Patent Citation 0001: GB 2372126 A (CODED ACCESS LTD). 2002-Aug.-14.
is an example of this type of system. A server accessible over the internet holds a secure database capable of generating an access code that will provide one time access to a known lock. Codes of other durations are also taught. In one suggested embodiment the code is calculated using an algorithm that takes as parameters the validity date/time and the lock number. The lock operates a similar algorithm to generate candidate codes in order to compare them to a received code. In order for the candidate codes to match the generated codes the parameters must be the same and this requires a clock in the lock.
Coded Access failed to implement a viable commercial system. Others including
Patent Citation 0002: WO WO 01/91074 A (MILLER). 2001-Nov.-29.
have suggested similar secure delivery systems with the common feature that it is the parcel itself which carries the “key” to unlock the secure container to which it will be delivered. Miller suggests the use of a barcode for the key.
The present applicant has also proposed a system described in
Patent Citation 0003: WO WO 2006/109097 A (DELIVERY WORKS LIMITED).
which relies on the master key being used in the generation of the single use transaction-unique delivery key and the storage of used keys within the lock. Delivery Works describes a delivery system comprising a combination lock providing access to a delivery space and an external delivery key generator, the lock comprising means for inputting a delivery key; processor means for validating the delivery key, means for releasing the lock in response to a valid delivery key, and storage means for identifying used delivery keys.Patent Citation 0004: U.S. Pat. No. 6,300,873 A (ATLANTES SERVICES INC). 2001-Oct.-09.
also describes a delivery system which is primarily directed to a system in which the locking device is in communication with a server that issues a delivery key. It also recognizes that it is desirable to have a stand-alone locking device and emphasises the desirability of one time single use codes that expire after use, but there is no disclosure of how this would work with a stand-alone locking device. The approach taken in this citation is maintaining identical access code tables at the server and locking devices. In the embodiment which uses a stand-alone locking device, the server and locking device each have a similar random number generator. This scheme cannot cope with the overlapping delivery/pickup scenario and the inventor suggests that several access codes are generated at a time by the server and the generator in the locking device. This is not a complete solution to the problem as, without communication, the locking device processor may recognize an access code ahead of the next code in the sequence but still within the window, it will then reject the earlier missed access code. There is no teaching as to how one-time use is achieved within this embodiment.